events

Abstract:

Humans are creating significant global environmental change, including shifts in climate, increased nitrogen (N) deposition, and the facilitation of species invasions. A multi-factorial field experiment is being performed in an arid grassland within the Sevilleta National Wildlife Refuge (NWR) to simulate increased nighttime temperature, higher N deposition, and heightened El Niño frequency (which increases winter precipitation by an average of 50%). The purpose of the experiment is to better understand the potential effects of environmental drivers on grassland community composition, aboveground net primary production and soil respiration. The focus is on the response of two dominant grasses (Bouteloua gracilis and B eriopoda), in an ecotone near their range margins and thus these species may be particularly susceptible to global environmental change.

It is hypothesized that warmer summer temperatures and increased evaporation will favor growth of black grama (Bouteloua eriopoda), a desert grass, but that increased winter precipitation and/or available nitrogen will favor the growth of blue grama (Bouteloua gracilis), a shortgrass prairie species. Treatment effects on limiting resources (soil moisture, nitrogen availability, species abundance, and net primary production (NPP) are all being measured to determine the interactive effects of key global change drivers on arid grassland plant community dynamics and ecosystem processes. This dataset shows values of soil moisture, soil temperature, and the CO2 flux of the amount of CO2 that has moved from soil to air.

On 4 August 2009 lightning ignited a ~3300 ha wildfire that burned through the experiment and its surroundings. Because desert grassland fires are patchy, not all of the replicate plots burned in the wildfire. Therefore, seven days after the wildfire was extinguished, the Sevilleta NWR Fire Crew thoroughly burned the remaining plots allowing us to assess experimentally the effects of interactions among multiple global change presses and a pulse disturbance on post-fire grassland dynamics.

Related sites:

Warming site

Methods:

Experimental Design

Our experimental design consists of three fully crossed factors (warming, increased winter precipitation, and N addition) in a completely randomized design, for a total of eight treatment combinations, with five replicates of each treatment combination, for a total of 40 plots. Each plot is 3 x 3.5 m. All plots contain B. eriopoda, B. gracilis and G. sarothrae. Our nighttime warming treatment is imposed using lightweight aluminum fabric shelters (mounted on rollers similar to a window shade) that are drawn across the warming plots each night to trap outgoing longwave radiation. The dataloggers controlling shelter movements are programmed to retract the shelters on nights when wind speeds exceed a threshold value (to prevent damage to shelters) and when rain is detected by a rain gauge or snow is detected by a leaf wetness sensor (to prevent an unintended rainout effect).

Each winter we impose an El Nino-like rainfall regime (50% increase over long-term average for non-El Nino years) using an irrigation system and RO water. El Nino rains are added in 6 experimental storm events that mimic actual El Nino winter-storm event size and frequency. During El Nino years we use ambient rainfall and do not impose experimental rainfall events. For N deposition, we add 2.0 g m-2 y-1 of N in the form of NH4NO3 because NH4 and NO3 contribute approximately equally to N deposition at SNWR (57% NH4 and 43% NO3; Bez et al., 2007). The NH4NO3 is dissolved in 12 liters of deionized water, equivalent to a 1 mm rainfall event, and applied with a backpack sprayer prior to the summer monsoon. Control plots receive the same amount of deionized water.

Soil Measurements

Soil temperature is measured with Campbell Scientific CS107 temperature probes buried at 2 and 8 cm In the soil. Soil volume water content, measured with Campbell Scientific CS616 TDR probes is an integrated measure of soil water availability from 0-15 cm deep in the soil. Soil CO2 is measured with Vaisala GM222 solid state CO2 sensors. For each plot, soil sensors are placed under the canopy of B. eriopoda at three depths: 2, 8, and 16 cm. Measurements are recorded every 15 minutes.

CO2 fluxes are calculated using the CO2, temperature, and moisture data, along with ancillary variables following the methods of Vargas et al (2012) Global Change Biology

Values of CO2 concentration are corrected for temperature and pressure using the ideal gas law according to the manufacturer (Vaisala). We calculate soil respiration using the flux-gradient method (Vargas et al. 2010) based on Fick’s law of diffusion where the diffusivity of CO2 is corrected for temperature and pressure (Jones 1992) and calculated as a function of soil moisture, porosity and texture (Moldrup et al. 1999).

Abstract:

The Monsoon Rainfall Manipulation Experiment (MRME) is designed to understand changes in ecosystem structure and function of a semiarid grassland caused by increased precipitation variability, by altering rainfall pulses, and thus soil moisture, that drive primary productivity, community composition, and ecosystem functioning. The overarching hypothesis being tested is that changes in event size and frequency will alter grassland productivity, ecosystem processes, and plant community dynamics. Treatments include (1) a monthly addition of 20 mm of rain in addition to ambient, and a weekly addition of 5 mm of rain in addition to ambient during the months of July, August and September. It is predicted that changes in event size and variability will alter grassland productivity, ecosystem processes, and plant community dynamics. In particular, we predict that many small events will increase soil CO2 effluxes by stimulating microbial processes but not plant growth, whereas a small number of large events will increase aboveground NPP and soil respiration by providing sufficient deep soil moisture to sustain plant growth for longer periods of time during the summer monsoon.

Related sites:

Monsoon (MRME) Site

Methods:

Experimental Design

MRME contains three ambient precipitation plots and five replicates of the following treatments: 1) ambient plus a weekly addition of 5 mm rainfall, 2) ambient plus a monthly addition of 20 mm rainfall. Rainfall is added during the monsoon season (July-Sept) by an overhead (7 m) system fitted with sprinkler heads that deliver rainfall quality droplets. At the end of the summer, each treatment has received the same total amount of added precipitation, delivered in different sized events. Each plot (9x14 m) includes subplots (2x2 m) that receive 50 kg N ha-1 y-1. Each year we measure: (1) seasonal (July, August, September, and October) soil N, (2) plant species composition and ANPP, (3) annual belowground production in permanently located root ingrowth cores, and (4) soil temperature, moisture and CO2 fluxes (using in situ solid state CO2 sensors).

Soil Measurements

Soil temperature is measured with Campbell Scientific CS107 temperature probes buried at 2 and 8 cm In the soil. Soil volume water content, measured with Campbell Scientific CS616 TDR probes is an integrated measure of soil water availability from 0-15 cm deep in the soil. Soil CO2 is measured with Vaisala GM222 solid state CO2 sensors. For each plot, soil sensors are placed under the canopy of B. eriopoda at three depths: 2, 8, and 16 cm. Measurements are recorded every 15 minutes.

CO2 fluxes are calculated using the CO2, temperature, and moisture data, along with ancillary variables following the methods of Vargas et al (2012) Global Change Biology

Values of CO2 concentration are corrected for temperature and pressure using the ideal gas law according to the manufacturer (Vaisala). We calculate soil respiration using the flux-gradient method (Vargas et al. 2010) based on Fick’s law of diffusion where the diffusivity of CO2 is corrected for temperature and pressure (Jones 1992) and calculated as a function of soil moisture, porosity and texture (Moldrup et al. 1999).

Abstract:

The Monsoon Rainfall Manipulation Experiment (MRME) is designed to understand changes in ecosystem structure and function of a semiarid grassland caused by increased precipitation variability, by altering rainfall pulses, and thus soil moisture, that drive primary productivity, community composition, and ecosystem functioning. The overarching hypothesis being tested is that changes in event size and frequency will alter grassland productivity, ecosystem processes, and plant community dynamics. Treatments include (1) a monthly addition of 20 mm of rain in addition to ambient, and a weekly addition of 5 mm of rain in addition to ambient during the months of July, August and September. We predict that soil N availability with interact with rainfall event size to alter net primary productivity during the summer monsoon. Specifically, productivity will be higher on fertilized relative to control plots, and productivity will be highest on N addition plots in treatments with a small number of large events because these events infiltrate deeper and soil moisture is available longer following large compared to small events.

Keywords:

Related sites:

Data sources:

Methods:

MRME contains three ambient precipitation plots and five replicates of the following treatments:
1) ambient plus a weekly addition of 5 mm rainfall, 2) ambient plus a monthly addition of 20 mm rainfall.

Rainfall is added during the monsoon season (July-Sept) by an overhead (7 m) system fitted with sprinkler heads that deliver rainfall quality droplets. At the end of the summer, each treatment has received the same total amount of added precipitation, delivered in different sized events.

On August 4th, 2009, lightning ignited a ~3300 ha wildfire that burned through the entire experiment and its surroundings allowing us to assess experimentally the effects of interactions among rainfall pulse dynamics and wildfire on post-fire grassland dynamics and ecosystem processes.

Additional information:

Data was not collected in 2011.

Additional Study Area Information

Study Area Name: Monsoon site
Study Area Location: Monsoon site is located just North of the grassland Drought plots
Vegetation: dominated by black grama (Bouteloua eriopoda), and other highly prevalent grasses include Sporabolus contractus, S.cryptandrus, S. lexuosus, Muhlenbergia aernicola and Bouteloua gracilis.

North Coordinate:34.20143
South Coordinate:34.20143
East Coordinate:-106.41489
West Coordinate:-106.41489

Abstract:

The purpose of this project is to test the hypothesis that the smallest 50% of precipitation events during the monsoon season affect microbial functioning and grassland productivity in mixed grasslands of B.eriopoda and B. gracilis at the SNWR. At the SNWR, the summer monsoon season accounts for 60% of total annual precipitation and drives the majority of vegetation productivity during the year; the largest 25% of precipitation events account for the majority of this precipitation. I predict that important ecological variables such as nutrient and soil moisture availability are disproportionately influenced by smaller events. The proposed project will help tease apart the importance of precipitation event classes on nutrient availability and grassland aboveground net primary production (ANPP). This research will also provide a basis for understanding how increased aridity in the U.S. southwest due to increasing global surface temperature and altered precipitation could affect grassland communities at the SNWR.

Related sites:

Deep Well Blue/Black Grama Mixed

Methods:

We will implement 10 open plots (control) and 10 precipitation exclosure plots(treatment; 20 total plots) at a mixed blue and black grama grassland site at the SNWR. In this experiment, treatment plots will only receive the largest 50% of precipitation events. This will maintain statistically similar total precipitation between control and treatment plots because the smallest 50% of events have an insignificant effect on total seasonal precipitation. How these small events are linked to microbial activity and vegetation productivity is still very much unknown. I predict that soil microbial activity and nutrient availability will differ between control and treatment plots and will result in differing vegetation ANPP between them. These effects may become more distinct as time progresses, which is the reason for conducting this research for a series of monsoon seasons.

Existing precipitation exclosures (2.45 m x 2.45 m) will be employed at the mixed grassland site. We will implement 20 total plots (10 control, 10 treatment; approx. 500 m2 total area). Temporary site infrastructure will include 10 precipitation exclosures, a water tank (1100 gal.) and soil moisture probes. This infrastructure currently exists at the mixed grassland site and will be adopted from Michell Thomey's project entitled, "Soil moisture extremes and soil water dynamics across a semiarid grassland ecotone."

Precipitation is the only independent variable in this experiment. Using precipitation exclosures, I will remove all ambient precipitation from treatment plots from DOY 182-273. Ambient daily precipitation thatexceeds the estimated 50% threshold will be delivered to the plots within 24 hours of an event. Delivered precipitation will be adjusted for atmospheric demand differences.

Dependent variables in this experiment are vegetation ANPP, soil nitrogen content, soil enzymatic activityand soil moisture content. Vegetation biomass will be collected from the sites on DOY 181 and 274. Soil enzymatic activity will be determined approximately 4 times per monsoon season using plot soil samples. Soil nitrogen content will be measured under vegetation using nitrogen probes. Volumetric soil moisture content [m3 m-3] will be measured continuously using soil moisture probes (30 cm depth).

Abstract:

In the southwestern United States two important seasons influence stream flow: snowmelt in spring and summer monsoonal rainfall events. Flow patterns exhibit peak discharge from snowmelt runoff in the spring followed by pulsed increases in stream discharge during late summer monsoons. Molles and Dahm showed the intensity of the snowmelt discharge is linked to El Nino-Southern Oscillation (ENSO) conditions in the tropical Pacific. El Nino and La Nina climate patterns also may affect late summer monsoonal precipitation in New Mexico by intensifying the monsoon during La Nina years and weakening monsoons during El Nino years. Stage gage data show seasonal and interannual variability in the intensity of snowmelt and monsoonal runoof events in montane catchments in New Mexico. Further, in-situ YSI sonde, Satlantic Submersible Ultraviolet Nitrate Analyzer (SUNA) and CycleP instrumentation show physical and chemical constituents respond to higher flow events driven by climate variability, and the constituents these instruments measure can be used as a proxy to estimate whole stream metabolism and nutrient cycling processes.

Abstract:

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded.

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID:

Core Areas:

Additional Project roles:

Keywords:

Related sites:

Five Points Black Grama Grassland (G)

Five Points Creosote (C)

Cerro Montoso Pinyon Juniper (P)

Methods:

Experimental design:

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots:

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.

Additional information:

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026

Study Area 1:

Study Area Name: Grass Endmember Plot

Study Area Location: Five Points Grass core site (exact point location of plot provided below)

Single Point:

North Coordinate: 34.339186

West Coordinate: -106.728303

Study Area 2:

Study Area Name: Creosote Endmember plot

Study Area Location: Five Points Creosote core site (exact point location of plot provided below)

Abstract:

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded.

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID:

Core Areas:

Additional Project roles:

Keywords:

Related sites:

Five Points Black Grama Grassland (G)

Five Points Creosote (C)

Cerro Montoso Pinyon Juniper (P)

Methods:

Experimental design:

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots:

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.

Additional information:

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026

Study Area 1:

Study Area Name: Grass Endmember Plot

Study Area Location: Five Points Grass core site (exact point location of plot provided below)

Single Point:

North Coordinate: 34.339186

West Coordinate: -106.728303

Study Area 2:

Study Area Name: Creosote Endmember plot

Study Area Location: Five Points Creosote core site (exact point location of plot provided below)

Abstract:

Dryland environments are estimated to cover around 40% of the global land surface, and are home to approximately 2.4 billion people. Many of these areas have recently experienced extensive land degradation. This study focuses on semi-arid areas in the US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into areas previously dominated by grasslands. This vegetation change has been associated with increases in soil erosion and water quality problems, including the loss of key nutrients such as carbon from the soil to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is lost as the land becomes more heavily degraded.

Therefore, understanding these vegetation transitions is significant both for sustainable land use and global biogeochemical cycling. This study uses an ecohydrological approach to develop an understanding of the relationship between structure and function across these transitions. This is done via the monitoring of rainfall-runoff events across instrumented runoff plots with different vegetation characteristics to investigate fluvial sediment fluxes during intense summer monsoon season rainfall events.

Data set ID:

Core Areas:

Additional Project roles:

Keywords:

Related sites:

Five Points Black Grama Grassland (G)

Five Points Creosote (C)

Cerro Montoso Pinyon Juniper (P)

Methods:

Experimental design:

Each study area consisted of a 10m wide, 30m long, downslope runoff plot, bound at the top and sides with aluminum flashing and fitted with water collecting guttering at the bottom so inputs and outputs could be quantified. The guttering fed water into a flume fixed into the ground at 4⁰ allowing water leaving the plot as runoff to be quantified.

The flumes were instrumented with a pump sampler to collect runoff samples leaving the plot and a bubbler module to measure discharge. In addition all runoff and associated sediment was collected in a covered stock tank (560 gallons for study area 1&2, 1000 gallons for study are 3). Rainfall onto the plot was measured using tipping-bucket rain gauges connected to the pump sampler. Following rainfall events all data was downloaded from the sampler using Flowlink v3.2 software.

Eroded sediment was collected from stock tank following rainfall events, coarse organic matter was removed via flotation, samples were oven dried at 60⁰C, weighed and sieved for particle size analysis using US. standard sieves at the Sevilleta LTER field station.

Setting up plots:

Plots were selected on comparable planar slopes in areas believed to be representative of endmember vegetation habitats.

Additional information:

This data was collected and analyzed by Alan Puttock as part of the PhD project: ‘Developing an understanding of vegetation change and fluvial carbon fluxes in semi-arid environments’. This project is supervised by Dr Richard Brazier, Dr Jenifer Dungait and Dr Kit Macleod. Analysis of samples/data is being carried out at the University of Exeter and North Wyke Research, United Kingdom.

This data was collected under USFWS permit number: 22522 10-026

Study Area 1:

Study Area Name: Grass Endmember Plot

Study Area Location: Five Points Grass core site (exact point location of plot provided below)

Single Point:

North Coordinate: 34.339186

West Coordinate: -106.728303

Study Area 2:

Study Area Name: Creosote Endmember plot

Study Area Location: Five Points Creosote core site (exact point location of plot provided below)

Abstract:

Microbes substantially control many biogeochemical processes in semiarid systems, including carbon and nitrogen fixation and carbon mineralization. Bacteria and fungi are osmotrophs that release enzymes into the environment to generate assimilable carbon and nutrients from organic particles. These enzymes are also the first agents to respond to pulses of soil moisture. The capacity to stabilize extracellular enzymes on soil particles preserves the utility of these nutrient-generating agents during extended dry periods. Enzyme stability can relate to environmental conditions and increase with clay mineral and humic compound concentrations. To better understand microbial response to precipitation variability, our objective was to determine the stability of extracellular enzymes under various monsoon precipitation regimes. During summer 2010, soil enzyme activity was measured in a rainfall manipulation study within a mixed-grass semiarid grassland in New Mexico, USA. Plots received either one large rain event or three evenly spaced small rain events per month. Before and after the first rain of each month, soil samples from the rhizosphere and from interspaces between plants were collected and analyzed for activity of four hydrolases; beta-glucosidase, beta-N-acetylglucosaminidase, leucine aminopeptidase, and alkaline phosphatase.

Additional Project roles:

Data set ID:

Core Areas:

Keywords:

Related sites:

Deep Well Blue/Black Grama Mixed

Methods:

For experimental design and precipitation manipulations see SEV218.

Before the first rain of each month, soil samples were collected from the rhizosphere and interspaces between plants. Four soil cores (1cm wide, 3 cm deep) were taken across the plot, with rhizoshpere samples from under B. eriopoda and B. gracilis, and mixed together for each sample. Enzyme activity in the rhizosphere and interspace were analyzed separately. Two hours after the rain event, soil samples were again collected in the same manner. Microbial response to precipitation is quick therefore 2 hours was ample time to assess microbial response. Samples were refrigerated and processed within 48 hours of collection to prevent enzyme degradation. Soils were subsampled for organic matter and water content. Field soil moisture was calculated by comparing weights of freshly collected soil and soil dried at 60 °C. A subsample was also burned at 500 °C for 4 hours to determine percent organic matter. The potential activity levels of beta-glucosidase, beta-N-acetylglucosaminidase, leucine aminopeptidase, alkaline phosphatase, and phenol oxidase were measured in the lab following the methods of Stursova et al. (2006).

Abstract:

Shrub expansion into grasslands can cause abrupt changes in ecosystem processes. Creosote (Larrea tridentata) is a native shrub in warm, arid deserts of the southwestern US and has taken over C4 grasslands. A limited freeze tolerance is thought to dictate the northern boundary of creosote and the Sevilleta National Wildlife Refuge occurs near to the northern extent of creosote. Cold temperatures are known to damage creosote. In laboratory trials, temperatures of -25 for 1 hour lead to xylem damaging embolism in nearly 100% of stems and temperatures of -24 C lead to seedling death in the lab. Sevilleta LTER meteorological data from a station located within creosote shrublands indicated a low temperature of -20 C between 1999 and 2010. On February 3, 2011 temperatures hit record lows in central New Mexico, reaching -30 C at shrublands within the SNWR. To address how creosote responds to a natural extreme cold events, plots were established to monitor creosote initial response and regrowth following the cold event. Initial surveys will determine canopy death and subsequent surveys of the same individuals will allow us to determine how creosote responds to record cold temperatures.

Core Areas:

Additional Project roles:

Data set ID:

Keywords:

Related sites:

South Gate Chihuahuan Desert

Red Tank Mixed Shrub/Juniper

Burn Exclosure (BurnX) Black Grama

Five Points Creosote (C)

Black Butte Mixed Grass

Methods:

Plots were established at 6 locations across SNWR. Criteria for site selection included the presence of L. tridentata, flat terrain to limit microtopographic impacts, close proximity to existing meteorological stations, and variation in shrub density between sites. At each site, approximately 200 shrubs were evaluated within circular plots (20m in diameter) with the number of plots at each site varying in shrub density. Initial surveys to determine canopy death were conducted in early April 2011. These surveys consisted of tagging each shrub with an unique ID, estimating canopy death, and measuring maximum canopy height, maximum width and the perpendicular width to max width.

Additional information:

Study Area 1:

Study Area Name: South Gate

Study Area Location: Located across the road from the met station located at South Gate.

Bounding Box:

North Coordinate: 34.42

South Coordinate: 34.19

East Coordinate: -106.513

West Coordinate: -107.08

Study Area 2:

Study Area Name: Microwave shrubland

Study Area Location: Located near the Microwave tower on the West side of the SNWR. Plots are located 100 to 200 m down the road just East of the tower towards Red Tank. Plots are on the West side of the road.

Bounding Box:

North Coordinate: 34.42

South Coordinate: 34.19

East Coordinate: -106.518

West Coordinate: -107.08

Study Area 3:

Study Area Name: BurnX shrubland site

Study Area Location: Located near Met station 52b, established near the burn enclosure (BurnX) Black Grama site.